Proposals for various types of multicolor imaging apparatus and techniques appear in the patent literature. There is described in Japanese Patent document 58002863 to Kawamura an image recording device for use in a color printer which include nozzle heads which spray liquid coloring toner onto electrostatic latent images on the side of a photosensitive drum and thus develop images thereon. A single nozzle is provided for each color and the nozzles reciprocate along a nozzle guide. Alternating current apparatus is disposed between the nozzle and the drum in order to spread out the impingement area of the toner on the drum.
U.S. Pat. No. 4,690,539 describes transfer apparatus in which a plurality of liquid images are transferred from a photoconductive member to a copy sheet. The liquid images, which include a liquid carrier having toner particles dispersed therein, are attracted from the photoconductive member to an intermediate web. A substantial amount of the liquid carrier is removed from the intermediate web and the toner particles are secured thereon. Thereafter, another liquid image having toner particles of a different color from the toner particles of the first liquid image is attracted to the intermediate member. Once again the liquid carrier material is removed from the web and the toner particles of the second liquid image are secured thereon. Thereafter, all of the toner particles are transferred from the intermediate member to the copy sheet, in image configuration.
U.S Pat. No. 3,900,003 describes a liquid developing device for use in multicolor electrophotographic copying machines, having a plurality of feed pipes for supplying different liquid color developers to a developing station, which feed pipes are connected to a common developer supply pipe. Valves are provided in the feed pipes wherein each of the valves are actuated by an electrical signal to supply only one selected liquid color developer to the developing station at a time. The liquid developing device is also provided with a belt for removing residual liquid developer remaining on an image bearing member after development and with a plurality of blades for scraping and collecting the thus removed liquid developer, which are selected and actuated in correspondence with a selected color.
U.S. Pat. No. 4,504,138 describes a method and apparatus for developing electrostatic latent images formed on a photoconductor surface providing the steps of applying a thin viscous layer of electrically charged toner particles to an applicator roller preferably by electrically assisted separation thereof from a liquid toner suspension. A restricted passage is defined between the applicator roller and the photoconductor surface approximately the thickness of the viscous layer and the toner particles are transferred from the applicator roller to the photoconductor surface due to their preferential adherence to the photoconductor surface under the dominant influence of the electric field of the electrostatic latent image carried by the photoconductive surface.
U.S. Pat. No. 4,400,079 describes a developing system for an electrophotographic copier in which a roller having a conductive outer surface is disposed adjacent to the imaging surface to form a gap. The roller is driven at a peripheral linear velocity substantially greater than the velocity of movement of the imaging surface and is supplied with liquid developer at a location spaced from the gap to cause the roller to inject the developer into the gap. The roller is coupled to a source of electrical potential.
U.S. Pat. No. 4,342,823 describes a perforate development electrode and a method for developing electrostatic images directly on a final image bearing sheet, formed of electrophotographic material coated onto a substrate, by means of a perforate development electrode and liquid toner, without immersing the material in a bath of toner. The method comprises spraying liquid toner against pressure reducing means adjacent to the electrode to reduce and make uniform the pressure of the flowing liquid toner and flowing the liquid toner uniformly over and through the perforate development electrode and over the image side of the sheet without contacting the side opposite the image side with the toner.
U.S. Pat. No. 4,233,385 describes a method of liquid development of charge images formed on a surface of a tape-like record carrier, for example by an electrostatic printer. The record carrier is simultaneously sprayed with developer liquid in two flows which are directed towards each other. As a result two separate, uniform and oppositely directed flow zones meeting at one common turbulent flow zone are obtained. Both during pre-development and final development the charge images are brought into contact with a large quantity of fresh developer liquid.
U.S. Pat. No. 4,073,266 describes apparatus for developing a latent electrostatic image on an electrophotographic copying material by means of a toner dispersion. An infeed roller applies the toner dispersion to the copying material and downstream thereof, a distribution roller acts on the surface of the copying material. Squeegee rollers downstream of the distribution roller effect removal of unused toner. Toner which adheres to the distribution roller during application of voltage thereto is sprayed off and recovered for recycling, the spraying agent being toner dispersion.
U.S. Pat. No. 3,405,683 describes apparatus for the development of latent electrostatic images on an electrophotographic material with a liquid developer which includes means to feed the electrophotographic material through a pair of rotatable nip rolls and nozzle means adapted to simultaneously spray the electrostatic image and the nip roll which contacts the latent image.
U.S. Pat. No. 3,867,708 describes a liquid toner system for developing an electrostatic image on a substrate in which liquid toner is supplied to a developer roller along its length by means of a header tube disposed parallel to the developer roller and having a plurality of feed holes along its length.
U.S. Pat. No. 4,522,484 describes a two stage development system. In the first stage a weak latent image on a photoconductor is developed by pumping liquid developer through a nozzle stated to be adapted to discharge the developer between the photoconductor and a reverse roller. The roller is biased to a potential greater than that of the background regions of the weak image and below that of the image regions of the weak image.